MANILA, Philippines -- Islamic militants holding three Red Cross workers hostage in the Philippines have extended a deadline they set to behead one of them, sources say.

Militants belonging to the Abu Sayyaf group Tuesday lengthened the deadline by three hours for Philippine military authorities to remove troops from several villages in the southern island-province of Sulu, an unnamed government source told the Philippine Daily Inquirer.

Abu Sayyaf has also kept communications open with Philippines Sen. Richard Gordon, head of the country's Red Cross, through text messages, GMA-TV reported Gordon telling a local radio interviewer Tuesday.

"I got a text right now from the person I have been in contact with," he reportedly said. "I am still not opening it and I cannot tell you the content."